Question: Which of the following numbers is a multiple of 7? ${51,91,92,108,114}$
Explanation: The multiples of $7$ are $7$ $14$ $21$ $28$ ..... In general, any number that leaves no remainder when divided by $7$ is considered a multiple of $7$ We can start by dividing each of our answer choices by $7$ $51 \div 7 = 7\text{ R }2$ $91 \div 7 = 13$ $92 \div 7 = 13\text{ R }1$ $108 \div 7 = 15\text{ R }3$ $114 \div 7 = 16\text{ R }2$ The only answer choice that leaves no remainder after the division is $91$ $ 13$ $7$ $91$ We can check our answer by looking at the prime factorization of both numbers. Notice that the prime factors of $7$ are contained within the prime factors of $91$ $91 = 7\times13 7 = 7$ Therefore the only multiple of $7$ out of our choices is $91$. We can say that $91$ is divisible by $7$.